Performance investigation and optimization of a microchannel heat exchanger with hybrid fins

Printed circuit board heat exchangers have demonstrated great potential for application in supercritical carbon dioxide Brayton cycles due to their highly efficient and compact structural characteristics. However, conventional single-fin designs often suffer from flow separation and stagnation under complex conditions, limiting thermal performance. This study introduces a novel hybrid fin design that integrates smooth airfoil and diamond-shaped fins. Using a unit microchannel model, the thermal-hydraulic performance of smooth airfoil, diamond-shaped, and hybrid fin channels was numerically evaluated. Results show that the hybrid configuration achieves synergistic balance between enhanced heat transfer and reduced flow resistance. Within an inlet mass flow rate of 0.00121-0.00323 kg/s, corresponding to Reynolds number of 3200-7200, the hybrid channel increases the Nusselt number by 16.5-10.4% and 9.2-4.6% compared to the smooth airfoil and diamond-shaped channels, respectively. Moreover, it exhibits improvements in the Nusselt number to the friction factor ratio of 5.7-10.7% over the smooth airfoil channel and 9.8-16.4% over the diamond-shaped channel. The overall thermo-hydraulic efficiency Q/?p, the ratio of the heat transfer rate to pressure drop, is also enhanced by 2.3-9.7% and 6.3-33.5%, respectively. Thus, the hybrid design effectively optimizes the trade-off between heat transfer and pressure drop, offering valuable insights for the structural design and parameter optimization of printed circuit heat exchangers.